Hitherto, many deaths and serious injuries have been caused by sudden deceleration of motor vehicles resulting either from sudden and violent brake action to avoid an impending collision or from an actual collision itself. Prior efforts have been made to cushion the front seat passengers (which term includes the driver) against the effects of being thrown forward against the door posts, windwhield header, windshield or steering wheel. One such effort has involved the so-called air bag device intended to suddenly inflate an air bag on or under the cowl but such air bag devices are of doubtful dependability in a collision, and provide no protection to the front seat passengers in the event of a sidewise roll-over of the vehicle. Moreover, such air bags do not hold the passengers either down against the seat bottom or against the seat back, and take the control of the vehicle out of the hands of the driver.